1. Field of the Invention
The present invention relates to a recording. head for use in a copier, a facsimile, wordprocessor, an output printer of terminal of host computer, or video output printer, in particular to a recording head and recording apparatus wherein an electrothermal converting element and a recording element are formed on a common substrate.
2. Related Background Art
Hitherto, there has been known a semiconductor device in which a plurality of semiconductor elements are arranged and are simultaneously or solely made operative, thereby controlling a current supply to each segment to be controlled.
FIG. 1A shows an example of such a semiconductor device. In the diagram, reference numeral 24 denotes an insulative substrate; 25 a semiconductor substrate; 26 an anode semiconductor region; 27 a cathode region.
The above semiconductor device has a feature such that it has a construction in which individual diodes are respectively arranged at intervals on the insulative substrate and are adhered thereto. Since the device has the above construction, a degree of freedom for a requirement of the standards for the diodes is large and a proper diode can be selected in a wide range in accordance with the use object. Further, since an electrical mutual interference between the diodes can be prevented, a high reverse bias voltage can be blocked by the insulative substrate and a large current can be supplied and a semiconductor device which has a high withstanding voltage and can endure a large current is realized.
FIG. 1B is a diagram showing an example of an electric circuit using the semiconductor device shown in FIG. 1A.
In such a circuit, for instance, to supply a current to a segment 28 such as a load resistor or the like, a switch 29 is closed, a positive potential H.sub.1 is biased, and further, a switch 30 is closed, thereby turning on a diode 31 corresponding to the segment to be supplied with a current. At this time, only the desired segment 28 can be solely made operative without influencing the other segments.
In the recording head also, the above described circuit structure is used. Respective segments, such as electrothermal converting elements, are electrically connected to respective diodes so that the segment can be solely made operative.
However, in the above conventional example, since the individual semiconductor elements have been arranged on the insulative substrate, there are the following technical problems.
1 Since the individual diodes are arranged on the insulative substrate one by one and are adhered thereto, the number of necessary steps is very large and the costs of the semiconductor device are high.
2 Since the individual diodes are used, there is a large deviation among the characteristics of the diodes. In the case of using a number of diodes, a degree of allowance cannot be set to a large value in consideration of the whole balance in designing of the system.
3 When executing the bonding to electrically couple the diodes, it is necessary to consider a space and a layout upon arrangement of the diodes and it is also necessary to provide gaps to electrically isolate the diodes. Thus, a yield per unit area decreases and the miniaturization of the whole semiconductor device is limited.
In order to solve the above problems 1-3, it seems desirable to form respective elements on a common substrate as disclosed in U.S. Pat. No. 4,429,321 (Matsumoto).
In the case where transistors are arranged in the semiconductor substrate and a circuit is constructed as shown in FIG. 1C, if there is a variation in current amplification factors of the transistors, a current concentration occurs in the diode having a large predetermined current amplification factor.
In the case where the above-mentioned semiconductor device is used in a recording head such as an ink jet recording head comprising a discharge opening to discharge an ink, a liquid passage communicated with the discharge port, and an electrical/thermal converting element serving as a discharge energy generating element which is provided within inside of or outside of a liquid path in correspondence to the discharge port or in a thermal head which is used for thermal copy transfer recording, thermal recording, or the like, it is difficult to avoid the enlargement and high costs of the recording head due to the above causes and, further, the whole recording apparatus increases in size and costs.
Particularly, in the recording head which is used in the ink jet recording apparatus, it has been found from many experiments that the construction of the recording head must be determined by sufficiently considering an influence by the heat which is generated in the semiconductor device, an influence by the heat generation of the electrical/thermal converting element, and the like in order to use a liquid (ink).
That is, when the head structure is such that the electrothermal converting element for generating thermal energy and the semiconductor functional elements are formed on a common semiconductor substrate, an image quality would vary greatly with an electric wiring, element structure and driving conditions. In concrete, a variation in emitted ink adhesion position on recording paper would be greatly changed. Therefore, in order to achieve high quality ink jet recording, a structure for minimizing the variation of dots is desired.